The most recent catastrophic event within the Caribbean has been a 7.3 magnitude earthquake that struck off the coast of Venezuela at 5:31pm on the 21st of August 2018. Countries such as Barbados, Guyana, Suriname, St. Lucia, and Dominica all experienced the shaking, with primary damage seemingly taking place in Venezuela and Trinidad & Tobago. With this in mind, I suspect that there will soon be a spike in conversation about seismic resistant structures in the upcoming months. That being said, I believe the discourse should span a wider scope to discuss the variety of hazards that Architects and Engineers design for on a daily basis.
When designing within the built environment, building codes typically reflect previously conducted vulnerability assessments and risk analysis of the geographical location. Appropriate structural systems and materials are then typically designed to conform to these building codes, which (once designed correctly) will extend the life of the structure and prevent collapse during a natural disaster.
In designing to mitigate natural disasters, structural and architectural detailing is imperative. The connection details of a structure can make or break a building's integrity. These construction systems allow for energy to transfer throughout the building and dissipate appropriately. Construction quality and material choices play a crucial role in this energy transfer and dissipation.
In the Caribbean region, we design for a number of different potential hazards. Below, I'll outline a few of the design considerations that Architects and Engineers deliberate when designing private homes to combat natural disasters.
1. Hurricane Resilience
(Rigid Structures with Little Uplift)
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| Buildings with a Destroyed Roofs in St. Maarten after Hurricane Irma, 2017. |
- Building foundations should be rigidly interconnected with floor systems.
- Building floor systems should be rigidly interconnected with wall systems.
- Wall systems should be rigid and reinforced.
- Wall systems should be rigidly interconnected with roof systems.
- Rigid roof systems.
- Roof systems with little to no eave overhang to prevent uplift.
- Adequate roof gradient to prevent uplift.
- Impact resistant windows and doors.
- Storm shuttering systems on all vulnerable windows and doors.
- Redundancy in safety strategies prevent uplift and missile impact throughout the structure.
2. Seismic Resilience
(Rigid or Flexible Structures with Adequate Energy Transfer)
(Rigid or Flexible Structures with Adequate Energy Transfer)
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| National Palace in Port-au-Prince, Haiti after the 7.0 Magnitude Earthquake, 2010. |
- Structure should have adequate vertical stiffness and strength.
- Structure should have adequate lateral stiffness and strength.
- Regularity, so the building moves equally to dissipate the energy.
- Deep, strong, stable foundations that are relative to context and rigidly interconnected with floor systems so they move as a unit.
- Structural and nonstructural components of the building interconnected so inertial forces dissipate.
- Multiple load bearing points sharing the forces to avoid foundations splitting.
- Redundancy in safety strategies to distribute mass and strength throughout the structure.
3. Tsunami/Storm Surge/Flood Resilience
(Hydrodynamic Forms and Elevated Protection)
(Hydrodynamic Forms and Elevated Protection)
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| Tsunami in Tokyo, Japan, 2011. |
- Structure should be oriented at an angle to the shoreline, as walls directly facing the ocean will suffer more damage.
- Deep, strong, stable foundations, braced at the footings to withstand erosion and scour when water retreats.
- Structure should be elevated to allow the water to go through the vertical supports (stilts) below floor level.
- Structure should have a hydrodynamic form to allow the water to go around the configuration.
- Rigid vertical supports to resist the force of the water or debris.
- Rigid wall systems to resist the force of the water or debris.
- Non-combustible materials to prevent the spread of fire from floating, burning debris.
- Structural connectors should be able to absorb stress.
- Redundancy in safety strategies to distribute mass and strength throughout the structure.
4. Differential Settlement/Subsidence Resilience
(Soil Testing and Appropriate Foundations)
(Soil Testing and Appropriate Foundations)
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| Residential Property in Britton's Hill, Barbados after Part of the Structure Collapsed into an Underground Cave, 2007. |
- Geotechnical assessment of site prior to construction to determine if soil contains sinkholes, has the potential for underground fluid withdrawal, hydrocompaction, or organic soil drainage and oxidation.
- Installation of stress-resistant utility lines and connections.
- Deep, strong, stable foundations that are relative to context and rigidly interconnected with floor systems so they move as a unit.
- Shear walls, geo-fabrics, and earth reinforcement techniques used to increase resistance to subsidence damage and to stabilize collapsible soils in retrofitted structures.
- Redundancy in safety strategies to distribute mass and strength throughout the structure.
5. Landslide/Mudslide Resilience
(Avoiding Hazardous Areas and Erosion Protection)
(Avoiding Hazardous Areas and Erosion Protection)
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| Residential Property Failing in a Landslide in Dominica During Tropical Storm Erika, 2015. |
- Developing in hazard prone areas avoided.
- Structural measures introduced to improve erosion protection.
- Structural measures introduced to improve drainage and channeling.
- Structural measures introduced to improve ground improvement, and vegetation.
- Buildings designed to withstand impact forces of landslides and to provide safe dwellings for people.
- Structure should be designed with evacuation routes.
6. Volcanic Eruption Resilience
(Designs to Withstand Ash Loading and Acid Corrosion)
(Designs to Withstand Ash Loading and Acid Corrosion)
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| Ash Accumulation on Rooftops in Plymouth, Montserrat after the Eruption in 1997. |
- Structure should be designed with evacuation routes.
- Structure should have adequate lateral stiffness and strength.
- Airtight sealed windows and doors to avoid ash penetration.
- Adequate roof gradient to prevent to shed most of the accumulated ash.
- Adequate structural design of roof system to account for the additional load of dry and wet ash.
- Reinforced concrete structures recommended.
- Roof should have simple geometry and materials to avoid ash capture.
- Guttering and drainage systems should be installed in ways to avoid accumulated debris that will stack on top of the roof and contribute to major structural collapse.
- Avoid materials that will easily corrode from acid rain and ash.
- External electronics should be wrapped in plastic to avoid corrosion and electronic discharge.
These are just a few strategies that are employed by professionals within the construction industry when designing to withstand the natural disasters within the region.
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For further details on any of the strategies provided above, please check out the references below:
REFERENCES:
WHOLE BUILDING DESIGN GUIDE (2017) Natural Hazards Mitigation [Online] Available from:
WHOLE BUILDING DESIGN GUIDE (2016) Seismic Design Principles [Online] Available from:
https://www.wbdg.org/resources/seismic-design-principles
EASTERN KENTUCKY UNIVERSITY (Unknown) 5 Tips To Building An Earthquake-Resistant Structure [Online] Available from: https://safetymanagement.eku.edu/resources/articles/5-tips-to-building-an-earthquake-resistant-structure/
PRILHOFER (Unknown) Earthquake-Resistant Construction With Pre-Cast Concrete Elements [Online] Available from: https://www.prilhofer.com/advantages-precast/earthquake-resistance
IMAGINATION STATION (Unknown) Earthquake-Proof Buildings [Online] Available from:
https://www.imaginationstationtoledo.org/educator/activities/can-you-build-an-earthquake-proof-building
ARCHITECT JAVED (Unknown) Building Stiffness and Earthquake Engineering [Online] Available from: http://articles.architectjaved.com/earthquake_resistant_structures/building-stiffness-and-flexibility-earthquake-engineering/
EASTERN KENTUCKY UNIVERSITY (Unknown) 5 Tips To Building An Earthquake-Resistant Structure [Online] Available from: https://safetymanagement.eku.edu/resources/articles/5-tips-to-building-an-earthquake-resistant-structure/
PRILHOFER (Unknown) Earthquake-Resistant Construction With Pre-Cast Concrete Elements [Online] Available from: https://www.prilhofer.com/advantages-precast/earthquake-resistance
IMAGINATION STATION (Unknown) Earthquake-Proof Buildings [Online] Available from:
https://www.imaginationstationtoledo.org/educator/activities/can-you-build-an-earthquake-proof-building
ARCHITECT JAVED (Unknown) Building Stiffness and Earthquake Engineering [Online] Available from: http://articles.architectjaved.com/earthquake_resistant_structures/building-stiffness-and-flexibility-earthquake-engineering/
THOUGHTCO (2017) About the Architecture of Tsunami Resistant Buildings [Online] Available from: https://www.thoughtco.com/architecture-of-tsunami-resistant-buildings-177703
BESTRUCTURAL (Unknown) Differential Settlement [Online] Available from: https://www.bestructural.com/differential-settlement/
WHOLE BUILDING DESIGN GUIDE (2017) Flood Resistance of the Building Envelope [Online] Available from: https://www.wbdg.org/resources/flood-resistance-building-envelope
CARIBBEAN HANDBOOK ON RISK INFORMATION MANAGEMENT (2016) Landslide Mitigation Measures for Buildings [Online] Available from: http://www.charim.net/use/331
ARCHITECTURE REVIVED (2015) How to Design Buildings to Withstand Volcanic Eruptions [Online] Available from: https://www.architecturerevived.com/how-to-design-buildings-for-volcano-eruptions/
Image 1 - Building With a Destroyed Roof in St. Maarten after Hurricane Irma, 2007.
Source: DAILY MAIL ONLINE (2017) Exclusive: Dramatic Footage of dEvastation Wreaked By Hurricane Irma as 'Entire' Caribbean Island of St. Maarten is Flattened [Online] Available from:
Image 2 - National Palace in Port-au-Prince, Haiti after the 7.0 Magnitude Earthquake, 2010.
Source: HAITI EARTHQUAKE CLEARING HOUSE (2010) Presidential Palace, Collapse of Central Dome [Online] Available from: http://eqclearinghouse.org/co/20100112-haiti/general-information/photos-by-amanda-lewis/attachment/_dsc0811
Image 3 - Tsunami in Tokyo, Japan, 2011.
Source: NEW VISION (2018) Japan Council Appeal Tsunami Death Compensation Rulings [Online] Available from: https://www.newvision.co.ug/new_vision/news/1477528/japan-councils-appeal-tsunami-death-compensation-rulings
Image 4 - Residential Property in Britton's Hill, Barbados after Part of the Structure Collapsed into an Underground Cave, 2007.
Source: BAJAN REPORTER (2007) Home Building Seminar at Yacht Club This Week - Avoid What Happened at Brittons Hill [Online] Available from: https://www.bajanreporter.com/2007/09/home-building-seminar-at-yacht-club-this-week-avoid-what-happened-at-brittons-hill/
Image 5 - Residential Property Failing in a Landslide in Dominica During Tropical Storm Erika, 2015.
Source: TELESUR TV (Unknown) Flood, Landslides In Dominica After Harsh Tropical Storm [Online] Available from: https://www.telesurtv.net/english/multimedia/Floods-Landslides-in-Dominica-After-Harsh-Tropical-Storm-20150827-0033.html
Image 6 - Ash Accumulation on Rooftops in Plymouth, Montserrat after the Eruption in 1997.
Source: THE ATLANTIC (2013) Soufriere Hills Volcano [Online] Available from: https://www.theatlantic.com/photo/2013/05/soufriere-hills-volcano/100509/
